1. Melt the butter in a stockpot over medium-high heat. Add the onion and celery and sauté, stirring frequently, for 7 minutes.

2. Add the chicken stock, wine, and potatoes. Simmer the soup just until the potatoes are tender, about 25 minutes.

3. Add the pears and arugula to the soup and simmer 5 minutes longer. Remove from the heat and stir in the light and heavy creams. Stir in the coriander. Process the soup in batches in a blender until smooth. Season to taste with salt and white pepper.

4. Refrigerate the soup until cold. To serve, ladle the cold soup into bowls and garnish each serving with a whole arugula leaf.